Geckos' hair-raising antics stick
Geckos, those small lizards that climb walls and hang from ceilings, are Post-its with four legs and a tail. And they may hold the key to designing dry adhesives that stick where other glues might fail.
A team led by Kellar Autumn, a biologist at Lewis & Clark College in Portland, Ore., says it has mimicked the gecko's ability to keep on sticking. It has synthesized the tiny hairs responsible for a gecko's ability to cling to just about anything.
Two years ago, researchers found that a gecko's foot is covered with 500,000 tiny hairs, each of which splits into as many as 1,000 tips so small that they interact with a surface on the molecular level. If a gecko were to able to use all of these tips at once, they could support 280 pounds, the researchers say.
The team used an atomic-force microscope to drill tiny holes into wax to act as molds. Then they cast the artificial hairs in silicone rubber and polyester resin. Experiments showed that the artificial hairs display a tiny amount of adhesion, half of which is attributable to the same forces acting between a gecko's foot hairs and a surface.
The team is now trying to build arrays of these artificial hairs to see if they can mimic a gecko's grip on a larger scale.
During the 1980s and early '90s, the Black Sea was an ecological basket case. Algae blooms smothered key fish stocks, and comb jellyfish, brought in via ship ballast water, ravaged other native fish.
These days, however, things are looking up, reports Ahmet Kideys, an associate professor with the Institute of Marine Sciences at the Middle East Technical University in Erdemli, Turkey. Writing in the current issue of Science, he notes that weak economies in former Iron Curtain countries, along with efforts to curb farm runoff into the Danube, Dnieper, and Dniester rivers, have cut fertilizer-nutrient concentrations in the coastal areas of the Black Sea by half or more since their peak in the early 1980s. As a result, bluefish and turbot stocks, once threatened by algae blooms, are recovering.
In 1997, ships inadvertently introduced a group of jellyfish that feed exclusively on comb jellies. After their food supply plunged, these newcomers also began to die, leaving the sea clear for anchovy stocks to recover, along with other barometers of the sea's ecological health.
Dr. Kideys holds that the Black Sea's relatively rapid recovery, while still a work in progress, should encourage efforts to save the Caspian Sea and other marine ecosystems "suffering from catastrophic threats."
Hydrogen often has been touted as the fuel of the future. It burns cleanly and, along with oxygen, can be used in fuel cells.
Now researchers at the University of Wisconsin at Madison have devised a way to extract hydrogen from sugars or alcohol, paving the way for harvesting plants to make hydrogen, rather than using natural gas or petroleum.
The process has the potential to be simpler and cheaper than extracting hydrogen from fossil fuels, the team says. The researchers refined glucose a ubiquitous sugar by passing it through a reactor that uses water and a platinum-based catalyst to facilitate the chemical reactions.
At least half the gas that emerged was hydrogen, along with carbon dioxide and trace amounts of methane, ethane, and propane. When the team used ethanol, a biomass-based alcohol, as a feedstock, the hydrogen yields reached 75 percent.
The technique would be climate-neutral, says Randy Cort-right, who led the chemical engineering team reporting its results in the Aug. 29 edition of the journal Nature. "The plant biomass grown for hydrogen production will fix and store the carbon dioxide released the previous year," he says.